You create a cone of deafening sound by clapping two limbs together.
Prerequisites: Str 30, Improved Unarmed Strike, Power Attack.
Benefit: You may, as a full-round action, clap two of your limbs together and create a cone of sound that starts at your position and continues out for a number of feet equal to 5 × your Hit Dice. A storm giant using this feat creates a cone 95 feet (5 × 19 Hit Dice) long. Creatures in the cone get a Fortitude save (DC 10 + ½ your Hit Dice + your Con modifier) to resist the effect. Those who fail their save are deafened for the duration of the encounter. Those who fail their save by 5 or more are also knocked prone.
Special: This effect automatically extinguishes unprotected flames (candles, torches, and the like).
Source: Savage Species, page 40. In Benefits, deleted the last sentence, changed “knocked down” to “knocked prone”, and hyperlinked the deafened and prone conditions to their descriptions.